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Related Concept Videos

Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

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Actin and myosin are contractile proteins that form the sarcomere found in skeletal muscle tissues for regulating muscle contraction. Actin, a globular contractile protein, interacts with myosin for muscle contraction. The skeletal tissue appears striped or striated under a microscope due to the repeated arrangement of contractile proteins actin and myosin along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes...
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Overview of Myosin Structure and Function01:15

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Myosins are a family of molecular motor proteins, first identified in the skeletal muscles, where they are responsible for muscle contraction. Along with their role in muscle contraction, these proteins also play a role in the intracellular transport of molecules and vesicles. There are twenty-four classes of myosins based on their domain sequence and organization. Of the twenty-four, six classes (Myosin I, Myosin II, Myosin V, Myosin VI, Myosin VII, and Myosin X)  have been well...
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Introduction to Actin01:26

Introduction to Actin

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Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution.  Actin coding genes are conserved within species and across...
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The Role of Actin and Myosin in Non-muscle Cells01:10

The Role of Actin and Myosin in Non-muscle Cells

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Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They  are held...
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Actin Polymerization and Cell Motility01:13

Actin Polymerization and Cell Motility

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Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate....
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The Sarcomere01:08

The Sarcomere

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A sarcomere is a microscopic segment repeating in a myofibril. The sarcomere fundamentally consists of two main myofilaments: thick filaments called myosin and thin filaments called actin. These filaments interact by sliding past each other in response to stimulus. In addition to myosin and actin, several other proteins, such as tropomyosin, troponin, titin, nebulin, myomesin, α-actinin, and dystrophin, play crucial roles in regulating, structuring, and functioning of the sarcomere.
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Aip1p Dynamics Are Altered by the R256H Mutation in Actin
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Distinct interactions between actin and essential myosin light chain isoforms.

Daria Petzhold1, Burcu Simsek1, Ralf Meißner1

  • 1Max-Delbrück-Center for Molecular Medicine, Dept. of Molecular Muscle Physiology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.

Biochemical and Biophysical Research Communications
|May 27, 2014
PubMed
Summary

Human cardiac myosin light chain isoforms exhibit distinct actin binding affinities. This difference in binding, particularly the lower affinity of atrial ELC, may influence muscle contraction dynamics.

Keywords:
Actin interactionEssential myosin light chainsSurface plasmon resonance

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Muscle Physiology

Background:

  • Myosin light chains (MLC) are crucial for muscle contraction.
  • The N-terminus of essential myosin light chains (ELC) interacts with actin, modulating myosin motor function.
  • Human cardiac muscle expresses different ELC isoforms, potentially leading to functional variations.

Purpose of the Study:

  • To investigate and compare the binding affinities of human atrial ELC (hALC-1) and ventricular ELC (hVLC-1) isoforms with actin.
  • To elucidate the kinetic parameters governing the interaction between these ELC isoforms and actin.
  • To understand how differential ELC isoform expression might affect cardiac muscle contractile activity.

Main Methods:

  • Recombinant human atrial and ventricular ELC isoforms (hALC-1, hVLC-1) were produced.
  • Circular Dichroism (CD) spectroscopy was used to assess the secondary structure and α-helicity of ELC isoforms.
  • Surface Plasmon Resonance (SPR) spectroscopy was employed to quantify the binding constants (affinity, association rates) between ELC isoforms and α-actin.

Main Results:

  • CD spectroscopy confirmed similar high α-helical content for both hALC-1 and hVLC-1.
  • SPR analysis revealed significantly lower affinity (higher KD value) of hALC-1 to α-actin (KD=575 nM) compared to hVLC-1 (KD=186 nM).
  • The reduced affinity of hALC-1 was primarily attributed to a significantly lower association rate (kon) compared to hVLC-1.

Conclusions:

  • Human atrial and ventricular ELC isoforms exhibit distinct binding kinetics with actin.
  • The differential interaction of ELC isoforms with actin provides a mechanism for modulating myosin motor function.
  • Isoform-specific regulation of ELC-actin binding may play a role in the functional specialization of cardiac muscle.